1. Field of the Invention
This invention relates to pipe couplings.
2. Related Art
Flange type pipe couplings require a substantial amount of space surrounding the coupling and numerous bolted fasteners and various seals to prevent leakage between the flange members. Various non-flange couplings occupying a smaller envelope have been proposed and in particular various clamping arrangements providing a coupling as strong as a flange coupling but occupying less space and offering reliable service. U.S. Pat. No. 3,403,931 to Crain et al. granted Oct. 1, 1998 provides an example of a clamp type pipe coupling or fitting. In addition, U.S. Pat. No. 3,404,902 granted to Latham et al. on Oct. 8, 1968 shows a clamp fitting in combination with a seal arrangement between the terminal ends of hub elements intended to be joined to pipe ends to enable a union to be formed between the hub elements. The principle underlying the clamp type pipe connector is the application of an axial force between pipe coupling elements created by radially compressing a clamp member over tapered faces of hub elements that effectively drives the mating halves of the hub assembly together to form a tight seal that is maintained by the clamp. If the clamp and the hub are made entirely of metal along with a seal that may be introduced between the hub ends, the coupling is able to withstand high temperatures and is capable of resisting high stress loads.
Other prior art devices for enabling coupling of pipe ends have been devised using a sliding sleeve or locking ring fitting over a split coupling that engages the pipe ends to be joined together. The ring effectively locks the coupling elements against axial separation while the coupling elements are retained in intimate contact with the pipe ends by the locking sleeve. An example of this type of coupling is shown in U.S. Pat. No. 5,131,632, British Patent No. 1 434 117 published May 5, 1976 and British Patent No. 1 133 351 published Nov. 13, 1968. However, typical prior art locking ring type couplings require modifying the configuration of the pipe ends to be joined together by machining notches or retainer grooves in the pipe ends or have other disadvantages that limit their application.
The present invention is a locking ring type coupling utilizing a pair of hub sections that are intended to be welded or otherwise permanently secured to the ends of pipe sections to be joined together by the coupling and wherein the hub sections include radially outwardly extending outer tapered surfaces that are engageable by surrounding annular split clamp elements that include inner tapered surfaces mating with the outer tapered surfaces of the hub sections. Driving the clamp elements radially inwardly draws the hub sections together in a tight union that resists bending loads and axial separation of the hub sections.
The clamp elements are radially compressed and locked together by an outer locking ring that may be manually installed or may be installed by means of a tool described herein. The use of the locking ring is facilitated by providing outer locking surfaces on the clamp elements that are relatively small in cross-section and which are provided with ramps that help guide the locking ring over the locking surfaces as the ring is placed in its operational position on the coupling. The locking ring, moreover, is provided with a motion stop surface that prevents advancement of the locking ring beyond a desired position and furthermore a retainer device may be provided to prevent unintentional motion of the locking ring in a direction tending to loosen the coupling. An internal metal seal may be provided that is clamped together with the mating hub sections when the coupling is fully assembled.
A tool for installing the locking ring includes an actuator that cooperates with coupling elements to drive the locking ring into position in a simple, convenient manner and also permits removal of the lock ring by using the same tool in a reverse position. The tool is configured so that it may be utilized with couplings of various diameters.